The LA Times reports on a lawsuit filed by citizens of California prescribed marijuana for medical purposes against their state's Department of Motor Vehicles for targeting them.

When Matt Vaughn was pulled over for speeding on Interstate 5 in
Northern California early on a Sunday morning, he had a bag of
marijuana on the passenger seat. The California Highway Patrol officer smelled the weed, searched the
car, took the marijuana and pipe and gave Vaughn a sobriety test, which
he passed. An angry Vaughn showed the officer his doctor's
recommendation to use marijuana for glaucoma. The officer was
unimpressed.

"He said, in Glenn County, they don't recognize those kinds of things,"
said Vaughn, 55, who has a long ponytail, mustache and beard. "He was
not very friendly about it." The 2005 incident cost Vaughn a speeding ticket, his 1 1/4 ounce of pot
and his driver's license -- and nine months of fighting the California
Department of Motor Vehicles -- before he prevailed.

As a result of that and other encounters involving medical marijuana,
an advocacy group has sued the DMV, asking for a written policy that
says medical marijuana should be treated the same as prescription drugs. The suit contends that the DMV has a pattern of investigating and
suspending the driver's licenses of people who use pot on the
recommendation of their doctors. It happens a disturbing amount," said Joseph D. Elford, chief counsel
for Americans for Safe Access, which promotes legalizing marijuana for
medicinal purposes and research. . . .

The DMV can obtain medical information about someone if an investigation is launched into the person's fitness to drive. In Vaughn's case, the CHP officer sent the DMV a report about Vaughn,
along with a medical journal article saying marijuana was not the
choice drug for treating glaucoma. In another case, Rose Johnson, 53, the plaintiff named in the pending
suit, used medical marijuana for back and neck injuries and lost her
license after a DMV worker referred her for an investigation. The worker had noted that Johnson had difficulty moving when she went
in to renew her driver's license. Despite her perfect driving record,
the DMV cited the Merced woman's marijuana use last year in revoking
her license, the suit said.

Elford said the DMV also learns of medical marijuana patients from
law enforcement officers who ask drivers if they have used drugs in the
24 hours before a traffic stop. Medical marijuana users usually answer truthfully, thinking they are
protected by law, Elford said. He added that he does not advise them to
lie because defrauding a police officer is a misdemeanor in California. State officials said in interviews that it is not their policy to take away licenses from marijuana patients. . . . Although medicinal weed is not automatic grounds for revoking a
license, conditions that impair safe driving, including "poor judgment,
aggressive behavior, impaired decision making, slowed motor functions,
impaired coordination . . . and drowsiness" could result in license
removal, he said.

Not even marijuana advocates recommend driving under pot's influence.
California has convicted drivers of being under the influence of
marijuana when they failed field sobriety tests, Elford said. Studies on the effects of marijuana on driving have reached varying
conclusions. Some found that experienced users are likely to compensate
for their deteriorated state by being especially cautious -- but are
prone to getting lost -- while others showed significant debilitating
effects from THC, the main mind-altering ingredient in marijuana. . . .